The invention relates to an improved framing element for a thermally insulated window sash and an improved thermally insulated window sash comprising the framing element. More specifically, the invention relates to such an improved framing element and window sash for a casement window.
Numerous types of window constructions have been used to reduce heat loss from a building or to reduce heat again into a building. One such window construction involves the use of storm windows, placed on the exterior of regular windows to minimize air leakage, heat transfer and undesired condensation on the window interior during cold weather.
Windows having two or more separated panes of glass with a dead air space therebetween that has been evacuated and sealed are known to have improved thermal insulation over single pane windows. However, the seals on such windows can break causing air leakage and moisture condensation between the panes of glass. Damaged panes in such windows can not be replaced without breaking the vacuum seal. Thus, the entire window sash must be replaced in such instances.
Further, thermal breaks, or sealed spaces of dead air within the sash, have been created in window sashes to minimize heat transfer through the window.
Metal sashes, made of materials such as aluminum, have been used for windows; however, because metals are good conductors of heat, condensation on the sashes often occurs. In addition, metals are prone to oxidation, scratching, pitting and denting. Thus, resinous plastic materials, such as vinyl, have been used for window sashes to reduce heat transfer through the window.
In U.S. patent application Ser. No. 632,910 filed July 20, 1984, I disclosed a thermally insulated window sash and sash element particularly for double-hung windows. The window sash element has a plurality of chambers wherein air is trapped and resists heat transfer through the window. Further, glass panes can easily be replaced in the sash by removal of a glazing strip used to secure the panes within the sash. U.S. patent application Ser. No. 632,910 is herein incorporated by reference.
While a number of the above-described advances in the art have improved thermal efficiency by reduced thermal conduction, air leakage and condensation, there remains a very real and subsantial need for further improvements in thermally insulated windows, particularly in thermally insulated casement windows.